Latent heat accumulators are materials which at certain temperatures undergo reversible thermodynamic state changes, for example solid/liquid phase transitions, and extract the associated enthalpy of phase change from the environment and, respectively, release said enthalpy into the environment. Latent heat accumulators can therefore prevent, or at least mitigate, temperature variations in the region of their thermodynamic state change, for example their melting point or freezing point. Examples of commonly used materials that accumulate latent heat are paraffin oils, fatty acids, and fatty waxes. Latent heat accumulators are used in a wide variety of applications: US 2001000517 describes the coating of textiles with materials of this type. U.S. Pat. No. 5,565,132 describes processes in which compositions comprising latent-heat-accumulating material, polymers, and silica particles are processed by way of a melt to give sheets, pellets, or fibers.
However, when latent heat accumulators are present in the liquid phase they are easily released into the environment. A frequent recommendation intended to prevent this is that latent-heat-accumulating material be sheathed with a higher-melting-point material, as described by way of example in US 2011169179A. WO 99/24525 teaches microcapsules in which a capsule wall made of highly crosslinked methacrylic ester polymers surrounds the latent-heat-accumulating material. US 2006272281, U.S. Pat. No. 8,070,876, WO11071402, and US 2011108241A describe the use of microcapsules of that type in construction applications. Another challenge consists in the further processing of these microcapsules to give marketable products, as discussed by way of example in EP1484378. The plastics technology sector makes very wide use of thermoplastic processes. However, a problem arising during the thermoplastic processing of the microcapsules is that a considerable proportion of the microcapsules is easily damaged, with the consequence that when the latent-heat-accumulating material undergoes transition to the liquid phase it can be released from the microcapsules into the environment, with resultant loss of the advantage of the microcapsules. Problems of this type arise by way of example during the thermoplastic processing of compositions which comprise polyurethane casting resins alongside the microcapsules.